Fin stabilized projectile



Feb. 4, 195s L. J. HANSEN ET AL FIN STABILIZED PROJETILE Filed July 9,1954 United States Patent() FIN STABILIZED PROJECTILE Lawrence J.Hansen, Palos Park, and Philip Rosenberg, Chicago, Ill., assignors, bymesne assignments, to the United States of America as represented by theSecretary of the Army Application July 9, 1954, Serial No. 442,456

3 Claims. (Cl. 102-50) The present invention relates to a n stabilizedartillery projectile.

More particularly, the invention relates to a lin stabilized artilleryprojectile provided with a compact, foldable n arrangement containablewithin a standard artillery cartridge `case and which will travelthrough a gun tube without appreciable damage to the bore.

Ammunition of this type generally is spin stabilized, and thoughoriginally intended for anti-aircraft defense, has also been adapted foruse against tanks and other ground targets as Well as water bornetargets by virtue of the incorporation of armor-piercing and highexplosive substances.

. For certain specific purposes, experience has indicated that betterarmor penetration, jet formation and more effective `destruction of aselected target is possible for lin stabilized (essentiallynon-rotating) rather than spinl stabilized projectiles, there beingimparted to the projectile, if desired, only suicient rotation of theorder of R. P. S.` to correct for manufacturing inaccuracies. An

important design consideration of any projectile in ight t is itsstability, and in a iin stabilized projectile a prime design factor isthe iin area since stabilization of the projectile in flight depends toa large degree upon the amount of air rushing past the tins. Inprojectiles of the nature contemplated, where lixed tins are used theouter diameter of the lin assembly is governed by the diametrallimitation imposed by the tapered forward end of the cartridge case,hence in order to achieve more elective iin area, theprojectile isprovided with a tapered boom section and decreased hub diameter. theabove described design the rear larger diameter end of the cartridgecase is usually provided with guide rails to engage the longitudinaledge of each tin in order 1) to prevent the tail fins from bearingagainst the side wall of the tapered cartridge case, (2) to guide theprojectile as it leaves the case, and (3) to cut down windage and yaw toobtain less departure of the projectile from true trajectory therebyinsuring less dispersion in tiring.

`The foldable iin type projectile may be designed to achieve all theaccuracy obtained by the prior art projectile without the use of guiderails. At the same time greater stabilization of the projectile in ightis possible since the area of the ns in unfolded position may beincreased considerably over the corresponding area of a iixed linprojectile.

It is4 accordinglyV an important aim of this invention to provide aprojectile having a compact, foldable iin arrangement receivable in astandard artillery cartridge case.

@It is alsoan important object of this invention to provide-a projectilehaving a compact, foldable lin arrange- Consequently in ment receivablein a standard artillery cartridge case, and

Another'paramount purpose of this invention is to provide a projectilehaving compact foldable tins pivotably mounted on the boat-tail of theprojectile, a differential pressure hollow piston translatable in theboattail of the projectile and a chamber to trap some of the propellentgases which in turn are released as the projectile is exposed toatmosphere to cause the piston to move rearwardly to thereby unfold thetins to fully open position.

A further consideration impelling the conception of this invention isthe provision of a projectile having a compact, foldable iin arrangementreceivable in a standard artillery cartridge case, and wherein thefoldable ins in fully open position present a larger n area toatmosphere than normally prevalent in a projectile of a similar typeusing tixed tins, wherefore greater stability of the projectile inflight or the same degree of stability with a shorter, more compactprojectile is achieved.

It is also in mind to provide a projectile having the above advantages,and also constructed and arranged to insure ease of assembly, handlingand storing.

Additional objects, advantages and features of the invention reside inthe construction, arrangement and com` bination of parts involved in theembodiment of the invention as will appear from the followingdescription and accompanying drawings, wherein:

Figure l is a side elevation, partly in section of an artilleryprojectile contained within a cartridge case,

Figure 2 is a longitudinal sectional View illustrating the projectileper se, the ns shown in folded position,

Figure 3 is an enlarged fragmentary sectional View, the

- fins shown in extended position,

Figure 4 is a cross section view taken on the line 4-4 of Figure 2.

Referring more particularly to the drawing wherein like referencecharacters have been used to designate similar or corresponding partsthroughout the several views, reference character 10 generallyrepresents an artillery shell having its rearward end containable withina standard artillery cartridge case 12.

The projectile details per se form no part of the present invention andmay be brieiiy described as comprising a central tubular portion 13,forwardly threaded internally at 14 to screw threadedly receive thereduced rear end of a forwardly tapering nose 16, into the forward endof which is screwed a spit back point detonating fuse 18 to complete theforward ogive of the projectile. The forf ward end of tubular portion 13approximately coextensively with its threaded portion 14 is seen as aslightly enlarged cylindrical annulus forming the forward bourrelet 20.Tubular portion 13 is'also provided with a thickened rear wall 22centrally apertured at 24 to screw threadedly receive aclosure plug 26,and extending axially forwardly forward bourrelet, and an axial ashpassage 34 extending between the apex of the conical cavity 32 and thebase detonator 28. The shaped cavity 32 is provided with a liner 36 inthe well known manner, the liner being extended as at 38 to line thepassage 34. The shell 10 is also provided with a second bourrelet 40spaced forwardly of the rear end of the shell to provide guidance forthe shell as it traverses the barrel bore as is well known.

The operation of this portion of the device is readily i apparent fromthe above description.

As the shell is tired the arming mechanism operates to place anexplosive lead (not shown) in base detonator 28 in the fully armedposition, i. e. in axial alinement with ash passage 34. Upon impact thepoint fuse 18 is initiated and the Patented Feb. 4, g

flash, and concussion of thev detonating.. wave` travels rearwardlythrough the hollow space formed by nose 16 and conical cavity 32, thenthrough the flash passage 3,4,` to set oifthe, base, detonator 28 whichvinl turnr is in` ashcommunicationwith the high explosive 3010- explodethe shell upon the desired target.

The fin assembly and fin actuating mechanism forming the hubof theinvention is mountedupon the boattail 42 of the projectile modifiedv toaccommodate the necessary elements. This modified boattail is` seen. asa spool like member 44 having a rear rim or flange 46, and a forward rim48 made integral with a. forwardly. extending elongated sleeveorcylindrical wall 50 adapted to snugly and tightly4 encompass the rearend of shell' 10which is reduced; in diameterA rearwardly of. rear.bourrelet 40 as at S2; cylindrical; wall 5,0,also presenting an. outerdiameter slightlysrnaller than bourrelet 40 toenablebourrelet 40 toengage the barrell bore. The boat tail 42 is secured to Shell soas toprovide a chamber 54 between the.. rear wall 22 and the forwardy faceofv riml 48', chamber 54 in turn communicating, witha. reduced axialbore 5,6 extending through spool 44, and into which isreceiveddifferential pressure piston 60.

As clearly seen in Figure 2 hollow piston 6.0 is a two part membercomprising a forward sleeve 62 which in stowed; iin position is arrangedso that a, portion of its rear surface slidingly engagesthe wall of bore56, and its forward portion annularly flanged at 64 to extend partiallyinto chamber 54. Flange 6,4 forms an annular stop ring to limit therearward travel of piston 60 in a manner to be later described. The rearend* of sleeve 62 is providedwith a threaded tenon 65 for screwthreadedly receiving the forward end of a second-sleeve 70 of piston 60which also slidingly engage the wall of bore 56, there being an annularspace 71 provided between the rear and forward ends of sleeves 62 and 70respectively, to receive an annular shear ring 72 integral with the wallofl-bore 56and extending radially into space 71, wherefore sleeves 62and 70 are normally locked against translation. To limit forwardmovement of piston 60, sleeve 70 is providedwith an annular flange 6Lwhich engages av shoulder 57 formed by enlarging the rearmost end ofbore 5.6,in spool 44. Sleeve 70 is in turn provided rearwardly with arearwardly extending conical wall 74 terminating in a rearwardly axiallyextending reduced boss 76 which is also provided with anoutwardly-struck rear flange 73 having front and rear beveled surfaces80, 82 respectively fora purpose to be later described, there being anaxial reduced bore or orifice 84 extending through boss 76 as plainlyseen in Figure 2. A plurality of bifurcated rearwardly extending lugs 86are secured in anyconvenient manner in circumferential array to the rearflat face of rim or flange 46 of spool 44, there being circumferentiallyalined bores formed in each bifurcated lug 86 to receive pinsv SSforpivotally mounting a iin 90 (see Figure 4), each fin 90 being anelongated fin section having a forward flat end 92 adapted to abut therear flat face of flange 46 and to extend radially inwardly to partiallyoverlie, bore 56 in spool 44 when the fins are in stowed position.

In this same stowed position the fins 90 are arranged so that acircumference corresponding to the leading edge of the tins is slightlyless than the maximum circumference of flange 46, and the forward outercorner of each viin is truncated as at 94 so that the fins may be freeto pivot outwardly by the rearward movement of piston 60 as later to bedescribed. The forward trailing edge of each fin (the inner edge instowed position as seen in Figure 2) normally abuts the side wall ofboss 76, there being recesses 96 formed in each said trailing edge inregistry with the flange 78, the recesses 96 being beveled to permit apredetermined rotation or folding outward of each iin whereupon there isengagement between flange 78 and the beveled surfaces of recess 96l tohold thetins in position. As shown in Figure 3 the unfolded position ofthe tins resultsA in approximately a 25 degree inclination between theleading edge and the longitudinal axis of the projectile.

The cartridge case 12 is provided with a large diameter elongatedcylindrical rear portion 100, a forward tapering portion 102 which inturn merges with a smaller diameter cylindrical extension 104. In4assembly extension 104 snugly engages the outer periphery of cylindricalwall 50 of spool member 44, and theouter peripheryy ofrear bourrelet 40,the forward end of extension 104 being crimped over the shoulder formedbetween bourrelet 40 and tubular shell wall 13. The fins normally are instowed or folded; positiony with hollow piston 60 held in its forwardposition by shear ring 72, The cartridge case 12 has been filled withpropellent 106 in the accepted manner, and the fins 90 are completelyembedded within the loosely packed propellant. It is important to noteat this time 'that forward sleeve 62 ofpiston 60- is provided with anoutwardly ared or tapered surface 108 extending between the respectiveforward and, rear opposed facesY of rim or flange. 48Y of spool 44 andannular flange 64 of piston sleeve 62.

ln operation the propellent powder 106 is ignited and the resultingpressure acts to propel the projectile. As this pressure. increases andthe shell travels the length o f the gun tube, orifice 84. admits someof the powder gas by way of hollow piston 60.into chamber 54 in theboattail. At. the same time the high differential pressure acting on therear surface of piston 60. holds the fin. and piston assembly in placetogether with shear ring 72, thereby counteracting 'the effects of setback forces. As the projectile leaves the muzzle of the gun the externalpres.- sure drops rapidly to. atmosphere while the gas pressure in thechamber of the, boattail remains relatively high. The entrapped pressurecauses piston 60 to move rearwardly shearing annular shear ring 72 andcausing tapered surface` 108 to engage the wall of bore 56 in spool 44.Ask piston 60 moves rearwardly the. beveled surfaces 80, 82. of flange78 which are in continuous engagement with the beveled edges ofrecesses96 in the tins 9,0 cause the fins 90 to pivot and move outwardly, thehigh pressure. in chamber 54 exerting an accelerating force on thepiston and fins before the interference resistance of the taper becomessuflicient to noticeably counteract the forces tending. to move thepiston. As the piston 60. continues. to move rearwardly the resistanceoffered by tapered sur.- face 108l increasel to effect decelerationofthe piston and iins to an extent to prevent overstressing of the,mechanism when stop ring 6,4,y seats against the rear face of flange 48o n spool 44. Also instrumental in easing thev loadf on the stop ring isthe decrease in energy of the trapped gases due to the work spent inmoving the piston, andthe pressure drop in the boattail chamber due tothe simultaneous escape of gases through orifice 84. Asl clear.- ly seenin Figure 3, in the fully opened, position, there is an angle ofapproximately 25 degrees between the leading edge of each nandthelongitudinalaxisof the projectile. The fins are locked ink this fullyopened position bythe keying` action between the beveled surfaces ofangev 78 and the bevelededges of recesses 96l in the/fins, andtheinterference fit between surface 1,08` of forward sleeve 62and the innersurface of axial bore 56, thus preventing the iins from folding inwardwhile the projectile is in ilight.

From the foregoing it is apparent that there has been described aprojectile having a compact, foldable lin arrangement receivable in astandard artillery case, wherein the foldable iins in fully openedposition present a larger n area to atmosphere than normally obtainablein a projectile having a fixed fin` arrangement, thereby achievinggreater stability in flight, and wherein a novel rack andl pinionmounting for each fin enables the fins to unfold positively and withoutthe risk of over-stressing the.

mechanism by virtue of the col-action rof the fins'with a differentialpressure piston received in the modified boattail of the projectile, andmovable in response to the pressure of the gases formed by thedetonation of the propellent charge.

While a specific embodiment of the invention has been shown anddescribed, it will be understood that various alterations may be madewithout departing from the spirit of the invention as indicated by thesub-joined claims.

We claim:

1. In a projectile of the type having a cartridge casing and shellportion comprising a boat-tail xed to the rear end of said shell andcarrying a plurality of nested eX- tensible stabilizing fins, saidboat-tail and said iins inclosed within said cartridge casing, said tinsbeing embedded n the propelling charge, an axial bore formed in saidboat-tail, a chamber formed in said boat-tail in axial alignment withsaid bore forwardly thereof and communicating therewith, a hollow pistonhaving a restricting orifice therein slidingly fitting said bore, therebeing shear pin means holding said piston in a forward position wherebythe forward portion of said piston extends within said chamber, theforward end of said piston within said chamber being tapered to anenlarged diameter at its forward end, said piston communicating uidunder pressure to said chamber upon ignition of said propelling charge,means at the rear end of said piston operatively associated with saidfins to extend said tins radially outwardly upon rearward movement ofsaid piston in response to dilerential pressure between said chamber andthe atmosphere, said piston being locked in rearward position by saidtapered portion and said bore.

2. A projectile comprising a hollow body and a boattailed rear end, ahollow piston having a restrictive orifice therein slidable in an axialbore formed in said boattail, a pluralityl of foldable stabilizing tinshingedly secured to the rear face of said boattail and overlying saidaxial bore, said fins adapted to nestle in folded position to present noprotrusion beyond the outside diameter of said hollow body, there beinga chamber formed in said boattail concentric about the forward end ofsaid hollov' piston, a cartridge casing and propelling charge thereinfor injecting fluid under pressure through said hollow piston and intosaid chamber, said piston adapted to slide axially rearwardly inresponse to differential pressure between said chamber and atmospherewhile said projectile is in ight, whereby said piston pivots said nsoutwardly to unfolded stabilizing position and means to lock said pistonin said rearward position.

3. A projectile adapted to be tired from a smooth bore weapon andcomprising, a hollow body having a boattailed rear end, a plurality ofradially disposed unfolding vanes pivotally mounted on pins secured incircumferential array on the bottom of said boattail, said vanes adaptedin folded position to enter the casing of a cartridge case forming partof said projectile, there being an axial bore formed in said boat-tailin open communication with an enlarged chamber concentric about theforward end thereof, a differential pressure piston in engagement withan overlying portion of each said vane, said piston having an axial boretherethrough with a restrictive orifice therein being axially rearwardlyslidable to unfold said vanes, releasable means retaining said piston invane folded position, a propellant charge in said cartridge caseinjecting a uid under pressure into said chamber through said pistonbore and adjacent the forward end of said piston to release said pistonfor movement into vane unfolding position and means to lock said pistonin said vane unfolded stabilizing position.

References Cited in the lile of this patent UNITED STATES PATENTS1,274,281 Kowalski July 30, 1918 2,613,605 Brandt Oct. 14, 1952 FOREIGNPATENTS 10,325 Great Britain of 1912 896,502 France Mar. 2, 1944 634,090Great Britain Mar. 15, 1950

